Impetigo is most often a staph infection, yes. Staphylococcus aureus is the primary bacterium behind the majority of impetigo cases today. But it’s not the only possible cause. Impetigo can also be caused by group A Streptococcus (the same bacteria behind strep throat), or by both bacteria at once.
Why Staph Is Now the Dominant Cause
Impetigo wasn’t always a predominantly staph-driven infection. Decades ago, group A Streptococcus was the more common culprit. Over time, the causative organism shifted toward Staphylococcus aureus, which now accounts for most cases. This shift has had a meaningful upside: one of the more serious complications of impetigo, a kidney condition called post-streptococcal glomerulonephritis, has become rarer as strep-caused cases have declined.
That said, strep still plays a role. Some cases involve strep alone, and others involve both strep and staph colonizing the same wound. From a treatment standpoint, the distinction usually doesn’t change what your doctor prescribes, since the standard antibiotics cover both bacteria. But the type of staph involved can matter, particularly when it comes to antibiotic resistance.
Two Types, One Staph Connection
Impetigo comes in two forms, and staph is central to both.
Non-bullous impetigo is the more common type, making up the majority of cases. It starts as small red sores, typically around the nose or mouth, that rupture and leave behind distinctive honey-colored crusts. Either staph or strep (or both) can cause it. The sores are superficial, staying in the outermost layer of skin, and they spread easily through direct contact.
Bullous impetigo is caused exclusively by Staphylococcus aureus. In this form, the bacteria produce exfoliative toxins that break down the connections between cells in the upper layer of skin. The result is large, fluid-filled blisters that are fragile and rupture easily. These tend to appear in skin folds and moist areas like the diaper region in infants or the armpits. Because a specific toxin drives the blistering, this form is always staph, never strep.
The MRSA Factor
Not all staph is the same. MRSA, the antibiotic-resistant strain of Staphylococcus aureus, has been isolated in as many as 20% of bullous impetigo cases. This is significant because MRSA doesn’t respond to many of the standard antibiotics typically used for skin infections. If impetigo isn’t improving after a few days of treatment, MRSA is one of the first things a doctor will consider. In those cases, a wound culture can identify the exact strain and guide a switch to an antibiotic that works.
What Impetigo Looks and Feels Like
The hallmark of non-bullous impetigo is honey-colored crusting over shallow sores. These usually appear on the face, especially around the nose and mouth, though they can show up anywhere skin has been broken by a cut, insect bite, or even eczema. The sores themselves aren’t typically painful, but they can be itchy, and scratching spreads the bacteria to new areas of skin.
Bullous impetigo looks different. Instead of crusty sores, you’ll see larger blisters filled with clear or yellowish fluid. When these blisters pop, they leave behind a raw, red base that may develop a varnish-like crust. Bullous impetigo is more common in newborns and young children, though adults can develop it too, particularly if their immune system is compromised.
Neither form typically causes fever or makes you feel sick overall. If you notice spreading redness, warmth, swelling beyond the sore itself, or fever, the infection may be moving deeper into the skin, which is a sign to get medical attention promptly.
How It Spreads
Impetigo is highly contagious. The bacteria spread through direct skin-to-skin contact with an infected person’s sores or through shared items like towels, clothing, or bedding. Children in daycare and school settings are especially vulnerable because of close contact and shared surfaces.
Once antibiotic treatment starts, contagiousness drops quickly. The CDC guidelines state that people with impetigo can return to school or work at least 12 hours after starting antibiotics. For certain situations, like healthcare workers or outbreak settings, waiting at least 24 hours is recommended. Until treatment begins, the sores remain contagious as long as they’re present.
Treatment and Recovery
Most mild impetigo is treated with a topical antibiotic applied directly to the sores. For cases with just a few small patches, this is often all that’s needed. You clean the area gently, removing crusts when possible, and apply the antibiotic ointment as directed, typically for about five to seven days.
Oral antibiotics become necessary when impetigo is widespread, when there are many lesions, or when topical treatment isn’t working. This is also where the MRSA question becomes practical: if a standard oral antibiotic doesn’t clear the infection within a few days, a culture can determine whether a resistant strain is involved and guide a switch to a more targeted option.
With appropriate treatment, impetigo typically clears within seven to ten days. Without treatment, mild cases may resolve on their own over two to three weeks, but the risk of spreading the infection to others and to new areas of your own skin makes treatment worthwhile.
Preventing Spread at Home
If someone in your household has impetigo, a few practical steps reduce the chance of it spreading. Give the infected person their own towels, washcloths, and bedding, and wash these items separately in hot water. Encourage frequent handwashing, especially after touching or treating the sores. Keep the affected skin loosely covered with gauze or a bandage when possible, and avoid sharing personal items like razors or sports equipment until the infection clears. Keeping fingernails trimmed short helps too, since bacteria collect under the nails during scratching and transfer easily to other skin or other people.